The present invention relates to an improved joint for tubular members of composite material. As used herein, composite material is intended to mean a fiber reinforced matrix system. Such systems are thought to have application to tubular members such as risers which are used in subsea oil and gas wells to extend from the subsea wellhead to the floating structure at the surface of the body of water, casings which are used to form the outer body or casing of rocket motors, pipe lines and other tubular members functioning to contain or conduct fluids.
In such tubular joints it is preferred that the joint have a uniform deflection in hoop tension along its length to avoid the previous problems of stiffness discontinuity and its impact on seal integrity. Stiffness discontinuity at a tubular joint can produce rotations of the two members relative to each other. Such relative rotations can result in a separation of the sealing surfaces, thus damaging or destroying the seal integrity.
A joint design for tubular members of composite materials is disclosed in the Overath et al U.S. Pat. No. 4,619,470. Each tubular member is formed of an inner jacket of thermoplastic material and an outer jacket of resin impregnated filament wound outer jacket with flanged sleeves threaded onto the rounded threads of the outer jacket at the ends of the two tubular members and having loose rings which are connected together by a plurality of bolts and nuts. A covering collar is provided on the inner end of each tubular member and has radial flange which is spaced from the radial flange of its opposite collar by a sealing member. A distance ring (spacer) is provided between the facing end of the flanges to establish the compression of the sealing member.
The Pierce U.S. Pat. No. 4,634,314 discloses a composite marine riser which includes a tubular body made of carbon or boron filaments embedded in a resin matrix (such as by filament winding) with a corrosion resistant inner sleeve, buoyancy material surrounding the body between radial ribs and surrounded by an outer shell and a water impermeable and non-galvanic active layer surrounding the outer shell. Metal flanges are used to connect riser sections.
The Ahlstone U.S. Pat. No. 3,768,842 discloses a light weight marine riser pipe of wound fiberglass coated with an epoxy or other suitable resin and includes steel connector members to connect adjoining sections together.
The Overath et al U.S. Pat. No. 4,614,369 discloses tubular members including an inner thermoplastic liner with an outer jacket of fiber winding impregnated with synthetic resin with rounded threads on the exterior of the ends of the outer jackets and half shells engaging within the threads on the outer jackets and held in position by clamping rings wedged upwardly on the tapers of the exterior of the half shells.
None of these prior art joints suggests the provision of a joint which would have a uniform hoop deflection along the length of the joint.